Adjustable cam unit

ABSTRACT

An adjustable cam unit adapted to be mounted on a cam shaft for rotation with the shaft comprising a hub adapted to be mounted on the shaft for rotation therewith, and an adjustable cam assembly on the hub comprising first and second cam disks, each having a peripheral notch, mounted on the hub for rotation on the axis of the hub to different positions of angular adjustment relative to one another to vary the conjoint peripheral notch defined by the peripheral notches of the two disks, and for conjoint rotation on the axis of the hub to vary the phase of the notch relative to the cam shaft. A switch-mounting plate is pivoted on the hub adapted to carry a switch for actuation by the cam assembly, with a special mounting permitting the switch to yield away from the cam assembly. The unit further includes releasable locks for retaining the disks in adjusted position on the hub.

Ficken et al,

[ ADJUSTABLE CAM UNIT [75] Inventors: Leonard A. lFicken, Manchester;

Gerald J. lPodgor-ny, St. Louis, both Primary Examiner-Samuel Scott Assistant Examiner-F. D. Shoemaker Attorney, Agent, or Firm-Keenig, Senniger, Powers and Leavitt of Mo.

[73] Assigneez illtllfilndustries, rm, New YoTIE, [57] ABSTRACT An adjustable cam unit adapted to be mounted on a [22] Filed: Apr. 6, 1973 cam shaft for rotation with the shaft comprising a hub adapted to be mounted on the shaft for rotation there- [211 App! 348764 with, and an adjustable cam assembly on the hub comprising first and second cam disks, each having a pe- [52] US. Cl 74/568 R, 74/568 M, 74/568 T ripheral notch, mounted on the hub for rotation on [5 1] Int. Cl. lFl6h 54/04 the axis of the hub to different positions of angular ad- [58] Field of Search 74/568 R, 568 M, 568 T justrnent relative to one another to vary the conjoint peripheral notch defined by the peripheral notches of v 6] References Cited the two disks, and for conjoint rotation on the axis of UN TE STATES PATENTS the hub to vary the phase of the notch relative to the 3 170 330 2/1965 cam shaft. A switch-mounting plate is pivoted on the 3:221:117 11 19 5 hub adapted to carry a switch for actuation by the 3 2 5 9 11/1966 cam assembly, with a special mounting permitting the 3,285,095 11 196 switch to yield away from the cam assembly. The unit 3,678,780 7/1972 Ponting r. 74/568 T further includes releasable locks for retaining the disks in adjusted position on the hub.

l5 Claims, 12 Drawing Figures 0/ I M 5 6/ s /5 //k/Z5 V 4 5 y'a l W 4/ a N7]; 0.2

PATENIEB W 1974 SIEUIUF 3 FIG.4

PATENIED 81974 3.839.925

sum aor a ADJUSTABLE CAM UNIT BACKGROUND OF THE INVENTION for switch-actuating use in a programmer for a vending machine such as shown, for example, in US. Pat. No. 3,446,137, but it will be understood that it is applicable to any adjustable cam usage.

SUMMARY OF THE INVENTION Among the several objects of the invention may be noted the provision of an adjustable cam unit constructed for mounting of a plurality of the units in close side-by-side relation on a cam shaft, the unit having cam means which is readily adjustable to vary its peripheral cam formation (e.g., the arcuate extent of a peripheral cam notch) as so mounted; the provision of such a unit wherein the cam means is adjustable not only as to peripheral cam formation but also as to phase with respect to the cam shaft; and the provision of such a unit for actuating a switch and including switchmounting means constructed to allow for relative wide tolerance in the mounting of the switch, avoiding problems ofjamming of the cam means or failure to actuate the switch.

In general, an adjustable cam unit of this invention is constructed for being mounted on a cam shaft for rotation with the shaft, comprising a hub adapted to be mounted on the shaft for rotation therewith, and adjustable cam means on the hub. The adjustable cam means comprises first and second cam elements each having a peripheral cam formation, at least one ofthese cam elements being mounted on the hub for rotation relative to the other on the axis of the hub to different positions of angular adjustment relative to the other to vary the conjoint peripheral cam formation defined by the peripheral cam formations of the two cam elements, means being provided for releasably locking said one cam element in adjusted position on the hub.

Other objects and features of this invention will be in part apparent and in part pointed out hereinafter.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. I is a section of an adjustable cam unit of this invention, taken on line I--I of FIG. 2;

FIG. 2 is an elevation of one face of the unit;

FIG. 3 is a view on a smaller scale of one face of a cam disk element of the unit;

FIG. 4 is an elevation on the scale of FIGS. 1 and 2 of the other face of the unit;

FIG. 5 is a view ofa switch-mounting bracket or per se;

FIG. 6 is a view of the opposite side of the plate from FIG. 5 showing how it is incorporated in the cam unit;

plate FIG. 7 is an end view of a programmer utilizing cam units of this invention, an end wall of the programmer being broken awayto show interior detail;

FIG. 8 is an elevation of the FIG. 7 programmer as viewed from the left of FIG. 7 with a front wall of the programmer broken away to show interior detail;

FIG. 9 is a section on line 99 of FIG. 4;

FIG. 10 is an enlarged detail showing how one of the two cam disk elements of the unit is locked in position;

FIG. 11 is an enlarged detail showing how the other of the two cam disk elements is locked in position; and

FIG. 12 is a view illustrating yielding of the switch plate (and switch thereon) away from the cam disk elements.

Corresponding reference characters indicate corresponding parts throughout the several views of the drawings.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to the drawings, there is indicated in its entirety at 1 an adjustable cam unit of this invention adapted to be mounted on a cam shaft 3 (see FIGS. 7 and 8) for rotation with the shaft. The unit 1 comprises a hub 5 adapted to be mounted on the shaft for rotation therewith. The hub comprises a tubular member having an axial opening 7 therein for receiving the shaft, and further having an integral flange 9 at one end thereof. At 11 is generally indicated an adjustable cam means on the hub comprising first and second cam elements DI and D2 each having a peripheral cam formation, and more particularly a peripheral notch extending approximately I of arc around the periphery of the element. The two cam elements DI and D2 are identical, each comprising a relatively thin cam disk; the peripheral notch in each of these cam disks-being designated 13. a

In accordance with this invention, at least one of these cam elements, for example the disk D2, is mounted on the hub for rotation relative to the other on the axis of the hub to different positions of angular adjustment relative to the other to vary the conjoint peripheral cam formation or notch indicated at N defined by the peripheral cam formations or notches 13 of the two cam elements or disks, and means indicated generally at 15 is provided for locking this one cam element in adjusted position on the hub. This locking means is accessible for release from the periphery of the unit I as will appear.

Preferably, as herein illustrated, both cam elements or disks DI and D2 are rotatable on the hub, the unit I having a retainer indicated generally at 17 for holding the disks D1 and D2 on the hub. The unit is assembled by applying disk D1 to the hub and sliding it against the flange 9, then applying disk D2 to the hub and sliding it against disk D], then applying the retainer 17 to hold the disks on the hub between the flange and the retainer. The locking means 15 for the disk D2 (which lies adjacent the retainer) is on the retainer. A second locking means I9 is provided for releasably locking the disk D1 in adjusted position on the hub, this second locking means being on the flange 9 of the hub (disk Dl lying against the flange). Like the first locking means 15, the'second locking means 19 is accessible for release from the periphery of the unit, as will appear.

The hub 5 with its flange 9, the cam disks D1 and D2, and the retainer 17 may all be molded of plastic material, such as a suitable nylon. The hub is molded with a main body portion 21 extending from one side (the inside) of the flange 9 and a relatively short extension 23 projecting from the other side (the outside) of the flange. The main body portion 21 is basically of circular cross-section but formed with an axial keyway 25 and a flat 27 on the side opposite the keyway. The axial opening 7 in the hub is shown as of square cross-section for reception on a cam shaft of square cross-section (shaft 3 being so formed), but it will be understood that it could be of any out-of-round cross-section for application to a shaft of corresponding out-of-round crosssection. Portion 21 of the hub is formed with a pair of recesses or notches 29 (see FIGS. 4 and 9) in the circular portions of its periphery extending laterally adjacent its free end for securing the retainer 17 to the hub as will appear.

Each of the cam disks D1 and D2 (which, as noted above, are identical) is a relatively thin disk basically of circular form but with the notch 13 extending for approximately 180 of are around its periphery, and having inclined ends 31 for the notch. The portion of the cam disk edge between the ends of the notch is designated 33. Each cam disk has a circular central opening 35 having a rotary fit on the main body portion 21 of the hub 5 and is formed with a concentric circular groove 37 in one face thereof. Each disk is provided with a circular toothed formation 39 at one face thereof, being formed with a concentric circular groove 41 in one face thereof with the outer side of this groove formed as a circular series of teeth providing said toothed formation. Disk D1 is applied to portion 21 of the hub 5 with its toothed groove 41 facing the flange 9, and disk D2 is applied to portion 21 of the hub with its toothed groove 41 facing away from disk D1 toward the free end of portion 21 and hence facing the retainer 17.

The retainer 17 is a relatively thin disk basically of circular form having a central opening 43 for receiving portion 21 of the hub. This opening is generally square but with a key 45 at the center of one of its four sides received in the keyway 25 to key the retainer to the hub to provide for rotation of the retainer with the hub. Additionally, the opposite side of the opening 43 engages the flat side 27 of the hub for further keying of the retainer to the hub. The retainer is formed with a pair of resilient detent means each designated 47 having a snap fit in a respective recess or notch 29, each of means 47 being formed by a slot 49 at one side of opening 43 in the retainer defining a relatively narrow resilient bridge piece having a central portion 51 adapted to snap into a respective recess 29 when the retainer is slid onto the free end of portion 21 of the hub. The length of portion 21 of the hub is generally equal to the sum of the thicknesses of the two cam disks D1 and D2 and the retainer disk 17 (see FIGS. 1 and 9) with the arrangement such that when the retainer disk 17 is snapped on the end of portion 21 of the hub to hold the two cam disks thereon, the outside face of the retainer disk is generally flush with the end of portion 21..

The locking means 15 for the disk D2 comprises a resilient latch member 53 constituted by a tongue extending generally radially outwardly from the central portion of the retainer 17 in a relatively deep radial notch 55 in the retainer. This tongue 53 is substantially thinnet than the retainer disk 17 and extends outwardly from the inner end of the notch adjacent the inside face of the retainer disk, iLe.-, its face toward cam disk D2 (see FIG. 1). The tongue 53 has a detent 57 adjacent its free end which is engageable between two adjacent teeth 39 of the cam disk D2, this detent being disengageable from the teeth by bending back the tongue.

The locking means 19 for the cam disk D1 is constituted by a resilient latch member 59 formed by an opening 61 in the flange 9 on the hub 5 adjacent the periphery of the flange. This opening 61 defines a resilient peripheral bridge piece constituting the stated resilient latch member, which is movable generally radially inwardly and outwardly, and which is formed with a detent 63 engageable between two adjacent teeth 39 of the cam disk D1. This detent 63 is disengageable from the teeth of D1 by pushing in the resilient bridge piece 59, inward movement of the latter (to prevent breaking it) being limited by a stop 65 formed on the inner side of opening 61.

As shown in FIG. 7, the unit 1 further comprises a switch mounting bracket 67 which is pivotally mounted on the hub 5 for swinging movement on the axis of the hub, and which is adapted to carry a switch 69 for actuation by the adjustable cam means 11 constituted by the cam disks D1 and D2. The bracket comprises a plate preferably molded of a suitable plastic such as nylon plastic having an opening 71 for receiving the extension 23 of the hub, the thickness of the bracket plate corresponding generally to the axial dimension of extension 23 so that the outside face of the plate 67 is generally flush with the outer end of the extension when the plate is applied to the extension with its inside face engaging the flange 9. Provision is made for yieldingly mounting the plate 67 on the hub via the opening 71 having a part-circular notch portion 73 receiving extension 23 of the hub with a resilient bridge piece 75 bounding the opening 71 opposite the notch 73 engaging extension 23. The bridge piece 75 is formed by a relatively narrow band of the material of the plate between th hub-receiving opening 71 and a second opening 77 in the plate outward of opening 71. The bridge piece is adapted resiliently to engage extension 23 to hold it in the part-circular notch 73 and to flex outwardly relative to the notch 73 for the yielding mounting of the plate 67 on the hub. Outward flexing of the bridge piece 75 relative to notch 73 is limited by a stop 79 to avoid its breaking. The plate 67 carries means for mounting a conventional switch 69 on the face of the plate toward the adjustable cam means 11, this means being illustrated as a pair of switch-locating pins 81 receivable in holes in the switch case, and a pair of bosses 83 adapted to receive screws 85 (see FIG. 7) for holding a switch in place. At 87 (FIG. 7) is indicated the operating arm of the switch having a follower roller 89 engaging the common periphery of the two cam disks D1 and D2, adapted to drop into the notch N defined by these two disks. The switch is mounted on the side of opening 71 opposite the resilient bridge piece 75. With the yielding mounting of the plate 67 on the hub 5, relatively wide tolerance in the mounting of the switch 69 is permitted, avoiding problems of jamming of the cam means 11 or failure to actuate the switch, noting that the switch is permitted to yield away from the cam means by flexing of the resilient bridge piece '75, as shown in FIG. i2.

H63. 7 and 8 illustrate a programmer generally designated 91 in which a plurality of the adjustable cam units it, including the switch bracket plates s"! carrying switches W, are mounted on cam shaft 3 of the programmer. The latter generally comprises a housing 93 in which is journalled cam shaft 3 of square crosssection for receiving the hubs 5 of the units 1, this shaft 3 being driven by a suitable motor (not shown). A bushing for the shaft is indicated at 95. The units i are positioned in side-by-side engagement on the shaft 3 between end walls 97 and 99 of th housing. The front lift and top W3 of the housing (front and. top as viewed in FIG. '7) are made removable in any suitable manner to enable each plate at to be swung out of the housing for access to the switch as carried by the plate 67 for servicing, e.g., for switch replacement. Each switch has prongs 1105 received in an electrical receptacle lit)? therefor in the housing when the switch plate is swung into the housing (there being a receptacle for each switch). A suitable means (not shown) may be provided for holding the switch plates at in place in the housing when the front and top Mill and 1 .03 are in place on the housing. Screws 35 need be used only for the switch 69 on the plate 67 at the right end of the programmer as viewed in MG. h, each other switch being held on the pins of its respective plate by the next unit l to the right.

With the front iltlili of the housing Q3 removed, the resilient latch tongue 53 of each unit ll is accessible from the front of the programmer for being flexed back to disengage detent 57 from the teeth of cam disk D2 (as shown in phantom in FIG. ll) so that the disk D2 may be turned on the respective hub 5 to vary the extent of the respective notch N. This is conveniently accomplished by inserting the tip of a screwdriver or some other suitable tool (or by using the fingernail) to pry back the tongue to withdraw the detent, the space provided by notch 55 in the retainer i? being sufficient for this purpose. The resilient bridge piece 5% of each unit t is also accessible from the front of the programmer for being flexed (via a suitable tool) to disengage detent 63 from the teeth 39 of disk Dll so that the latter may be turned on the hub. Generally, disk D2 is adjusted for varying the extent of the notch N, and disks D11 and D2 may be conjointly rotated without relative rotation on the hub for adjustment of the phase of the notch N relative to the cam shaft 3.

in view of the above, it will be seen that the several objects of the invention are achieved and other advantageous results attained.

As various changes could be made in the above con structions without departing from the scope of the invention, it is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.

What is claimed is:

B. An adjustable cam unit adapted to be mounted on a cam shaft for rotation with the shaft comprising a hub adapted to be mounted on the shaft for rotation therewith, adjustable cam means on the hub comprising first and second cam elements each having a peripheral cam formation, both said cam elements being mounted on the hub for rotation relative to one another on the axis of the hub to different positions of angular adjustment relative to each other to vary the conjoint peripheral cam formation defined by the peripheral cam formations of the two cam elements, a retainer on the hub for holding the cam elements on the hub, first locking means for releasably locking said first cam element in adjusted position on the hub, and second locking means for releasably locking the second cam element in adjusted position on the hub, the first locking means being an integral part of the retainer and the second being on the hub.

2. An adjustable cam unit as set forth in claim 1 wherein the peripheral cam formation of each cam element comprises a notch, the two notches of the two cam elements conjointly defining; a peripheral cam notch the arcuate extent of which may be varied by the relative rotation of the cam elements, and the phase of which may be varied by rotation of both cam elements on the hub.

3. An adjustable cam unit as set forth in claim ll wherein the hub is a tubular member having an axial opening for receiving a cam shaft with the hub rotatable with the shaft, said hub having a flange adjacent one end thereof and said retainer being secured on the other end of the hub with said cam elements between the flange and the retainer.

4. An adjustable cam unit adapted to be mounted on a cam shaft for rotation with the shaft comprising a hub adapted to be mounted on the shaft for rotation therewith, adjustable cam means on the hub comprising first and second cam elements each having a peripheral cam formation, at least one of said cam elements being mounted on the hub for rotation relative to the other on the axis of the hub to different positions of angular adjustment relative to the other to vary the conjoint peripheral cam formation defined by the peripheral cam formations of the two cam elements, and means for releasably locking said one cam element in adjusted position on the hub, wherein both cam elements are rotatable on the hub, said unit having a retainer on the hub for holding the cam elements on the hub, and having a second locking means for releasably locking the other cam element in adjusted position on the hub, the first locking means being on the retainer and the second being on the hub, wherein the hub is a tubular member having an axial opening for receiving a cam shaft with the hub rotatable with the shaft, said hub having a flange adjacent one end thereof and said retainer being secured on the other end of the hub with said cam elements between the flange and the retainer, and wherein the hub has at least one peripheral recess adjacent its said other end and the retainer comprises a disk having a resilient detent means having a snap fit in said recess.

5. An adjustable cam unit as set forth in claim d wherein the hub and retainer are formed to provide for rotation of the retainer with the hub.

d. An adjustable cam unit as set forth in claim wherein said disk has a central opening for receiving the hub and the resilient detent means is formed by at least one slot at one side of the central opening defining a resilient bridge piece adapted to snap into said recess.

'7. An adjustable cam unit as set forth in claim 3 wherein the axial opening in the hub is out-of-round for application to an out-of-round cam shaft.

8. An adjustable cam unit adapted tobe mounted on a cam shaft for rotation with the shaft comprising a hub V adapted to be mounted on the shaft for rotation therewith, adjustable cam means on the hub comprising first and second cam elements each having a peripheral cam formation, at least one of said cam elements being mounted on the hub for rotation relative to the other on the axis of the hub to different positions of angular adjustment relative to the other to vary the conjoint peripheral cam formation defined by the peripheral cam formations of the two cam elements, and means for releasably locking said one cam element in adjusted position on the hub, wherein both cam elements are rotatable on the hub, said unit having a retainer on the hub for holding the cam elements on the hub, and having a second locking means for releasably locking the other cam element in adjusted position on the hub, the first locking means being on the retainer and the second being on the hub, wherein the hub is a tubular member having an axial opening for receiving a cam shaft with the hub rotatable with the shaft, said hub having a flange adjacent one end thereof and said retainer being secured on the other end of the hub with said cam elements between the flange and the retainer, and wherein the cam elements are identical, each comprising a cam disk having a circular toothed formation at one face thereof, one cam disk being arranged with its said toothed formation facing the retainer and the other being arranged with its said toothed formation facing the flange, the first locking means including a resilient latch member on the retainer having a detent engageable between two adjacent teeth of the first cam disk, and the second locking means including a resilient latch member on the flange having a detent engageable between the two adjacent teeth of the second cam disk.

disk.

11. An adjustable cam unit as set forth in claim 8 wherein each cam disk has a peripheral notch, the two notches of the two cam disks conjointly defining a peripheral cam notch the arcuate extent of which may be varied by the relative rotation of the cam elements, and the phase of which may be varied by rotation of both cam elements on the hub, each cam disk having a concentric circular groove in one face thereof, said one disk being arranged with its grooved face toward the retainer and the other being arranged with its grooved face toward said flange, the teeth of each cam disk being in the outer side of its said groove.

12. An adjustable cam unit adapted to be mounted on a cam shaft for rotation with the shaft comprising a hub adapted to be mounted on the shaft for rotation therewith, adjustable cam means on the hub comprising first and second cam elements each having a peripheral cam formation, at least one of said cam elements being mounted on the hub for rotation relative to the other on the axis of the hub to different positions of angular adjustment relative to the other to vary the conjoint peripheral cam formation defined by the peripheral cam formations of the two cam elements, means for releasably locking said one cam element in adjusted position on the hub, and a bracket pivotally mounted on the hub for swinging movement on the axis of the hub, said bracket being adapted to carry a switch for actuation by said adjustable cam means.

13. An adjustable cam unit as set forth in claim 12 having means for yieldingly mounting the bracket on the hub.

14. An adjustable cam unit as set forth in claim 13 wherein the bracket comprises a plate and said yielding mounting means comprises an opening in the plate having a part-circular notch portion receiving the hub and a resilient bridge piece bounding said opening opposite the notch and engaging the hub.

15. An adjustable cam unit as set forth in claim 14 wherein said bridge piece is formed by a relatively narrow band of the material of the plate between said hubreceiving opening and a second opening outward of said hub-receiving opening. 

1. An adjustable cam unit adapted to be mounted on a cam shaft for rotation with the shaft comprising a hub adapted to be mounted on the shaft for rotation therewith, adjustable cam means on the hub comprising first and second cam elements each having a peripheral cam formation, both said cam elements being mounted on the hub for rotation relative to one another on the axis of the hub to different positions of angular adjustment relative to each other to vary the conjoint peripheral cam formation defined by the peripheral cam formations of the two cam elements, a retainer on the hub for holding the cam elements on the hub, first locking means for releasably locking said first cam element in adjusted position on the hub, and second locking means for releasably locking the second cam element in adjusted position on the hub, the first locking means being an integral part of the retainer and the second being on the hub.
 2. An adjustable cam unit as set forth in claim 1 wherein the peripheral cam formation of each cam element comprises a notch, the two notches of the two cam elements conjointly defining a peripheral cam notch the arcuate extent of which may be varied by the relative rotation of the cam elements, and the phase of which may be varied by rotation of both cam elements on the hub.
 3. An adjustable cam unit as set forth in claim 1 wherein the hub is a tubular member having an axial opening for receiving a cam shaft with the hub rotatable with the shaft, said hub having a flange adjacent one end thereof and said retainer being secured on the other end of the hub with said cam elements between the flange and the retainer.
 4. An adjustable cam unit adapted to be mounted on a cam shaft for rotation with the shaft comprising a hub adapted to be mounted on the shaft for rotation therewith, adjustable cam means on the hub comprising first and second cam elements each having a peripheral cam formation, at least one of said cam elements being mounted on the hub for rotation relative to the other on the axis of the hub to different positions of angular adjustment relative to the other to vary the conjoint peripheral cam formation defined by the peripheral cam formations of the two cam elements, and means for releasably locking said one caM element in adjusted position on the hub, wherein both cam elements are rotatable on the hub, said unit having a retainer on the hub for holding the cam elements on the hub, and having a second locking means for releasably locking the other cam element in adjusted position on the hub, the first locking means being on the retainer and the second being on the hub, wherein the hub is a tubular member having an axial opening for receiving a cam shaft with the hub rotatable with the shaft, said hub having a flange adjacent one end thereof and said retainer being secured on the other end of the hub with said cam elements between the flange and the retainer, and wherein the hub has at least one peripheral recess adjacent its said other end and the retainer comprises a disk having a resilient detent means having a snap fit in said recess.
 5. An adjustable cam unit as set forth in claim 4 wherein the hub and retainer are formed to provide for rotation of the retainer with the hub.
 6. An adjustable cam unit as set forth in claim 5 wherein said disk has a central opening for receiving the hub and the resilient detent means is formed by at least one slot at one side of the central opening defining a resilient bridge piece adapted to snap into said recess.
 7. An adjustable cam unit as set forth in claim 3 wherein the axial opening in the hub is out-of-round for application to an out-of-round cam shaft.
 8. An adjustable cam unit adapted to be mounted on a cam shaft for rotation with the shaft comprising a hub adapted to be mounted on the shaft for rotation therewith, adjustable cam means on the hub comprising first and second cam elements each having a peripheral cam formation, at least one of said cam elements being mounted on the hub for rotation relative to the other on the axis of the hub to different positions of angular adjustment relative to the other to vary the conjoint peripheral cam formation defined by the peripheral cam formations of the two cam elements, and means for releasably locking said one cam element in adjusted position on the hub, wherein both cam elements are rotatable on the hub, said unit having a retainer on the hub for holding the cam elements on the hub, and having a second locking means for releasably locking the other cam element in adjusted position on the hub, the first locking means being on the retainer and the second being on the hub, wherein the hub is a tubular member having an axial opening for receiving a cam shaft with the hub rotatable with the shaft, said hub having a flange adjacent one end thereof and said retainer being secured on the other end of the hub with said cam elements between the flange and the retainer, and wherein the cam elements are identical, each comprising a cam disk having a circular toothed formation at one face thereof, one cam disk being arranged with its said toothed formation facing the retainer and the other being arranged with its said toothed formation facing the flange, the first locking means including a resilient latch member on the retainer having a detent engageable between two adjacent teeth of the first cam disk, and the second locking means including a resilient latch member on the flange having a detent engageable between the two adjacent teeth of the second cam disk.
 9. An adjustable cam unit as set forth in claim 8 wherein the resilient latch member on the retainer is constituted by a tongue extending generally radially in respect to the retainer.
 10. An adjustable cam unit as set forth in claim 8 wherein the resilient latch member on the flange is formed by an opening in the flange adjacent its periphery defining a resilient peripheral bridge piece, the latter being movable generally radially inwardly and outwardly and formed with the detent for the second cam disk.
 11. An adjustable cam unit as set forth in claim 8 wherein each cam disk has a peripheral notch, the two notches of the two cam disks conjointly defining a peripheral cam notch the arcuate extent of which may be varied by The relative rotation of the cam elements, and the phase of which may be varied by rotation of both cam elements on the hub, each cam disk having a concentric circular groove in one face thereof, said one disk being arranged with its grooved face toward the retainer and the other being arranged with its grooved face toward said flange, the teeth of each cam disk being in the outer side of its said groove.
 12. An adjustable cam unit adapted to be mounted on a cam shaft for rotation with the shaft comprising a hub adapted to be mounted on the shaft for rotation therewith, adjustable cam means on the hub comprising first and second cam elements each having a peripheral cam formation, at least one of said cam elements being mounted on the hub for rotation relative to the other on the axis of the hub to different positions of angular adjustment relative to the other to vary the conjoint peripheral cam formation defined by the peripheral cam formations of the two cam elements, means for releasably locking said one cam element in adjusted position on the hub, and a bracket pivotally mounted on the hub for swinging movement on the axis of the hub, said bracket being adapted to carry a switch for actuation by said adjustable cam means.
 13. An adjustable cam unit as set forth in claim 12 having means for yieldingly mounting the bracket on the hub.
 14. An adjustable cam unit as set forth in claim 13 wherein the bracket comprises a plate and said yielding mounting means comprises an opening in the plate having a part-circular notch portion receiving the hub and a resilient bridge piece bounding said opening opposite the notch and engaging the hub.
 15. An adjustable cam unit as set forth in claim 14 wherein said bridge piece is formed by a relatively narrow band of the material of the plate between said hub-receiving opening and a second opening outward of said hub-receiving opening. 